Appeal 3361634

The appeal is allowed and planning permission is granted for the erection of air source heat pumps/air conditioning unit and acoustic enclosure at The Gatehouse, [site address] , [site address] , [postcode] in accordance with the terms of the application, Ref 24/01209/HOU, and the plans submitted with it, subject to the conditions set out in the schedule attached to this decision.

The description for the development as set out in the application form and the council’s decision notice refer to part of the proposal being retrospective. As permission cannot be granted retrospectively, I have deleted this from the description used in this decision.

In their decision notice the Council refer to paragraph 135 of the 2023 National Planning Policy Framework (the Framework). This has since been revised and the current Framework was published in December 2024. In the current Framework paragraph 135 of the 2023 publication remains unchanged. I confirm that in this decision I refer to the 2024 Framework, which is referred to by the appellant in their appeal statement.

The main issue is the effect of the proposal on the living conditions of the occupiers of [address] due to noise and disturbance.

The appeal site is located within a private residential road that is characterised by large family homes set within generous sized and mature landscaped plots. As confirmed by the noise assessments carried out by the Council and on behalf of the appellant and the occupiers of [address], noise levels within the immediate area are low.

The proposed air source heat pumps (ASHPs) and air conditioning unit (ACU) have already been installed. They are located adjacent to a domestic building within the appeal site and a short distance from the boundary with [address]. The proposed ASHPs and ACU are currently enclosed by fencing which would be re-erected along two sides of the proposed acoustic enclosure. This fencing has the appearance of a tall domestic fence. Although the proposed louvres on the south west elevation would be utilitarian in appearance, they would be green in colour and discretely located.

In principle the Council raises no objections to the installation of ASHPs, which accord with the sustainability objectives of Policies CS1 and DM2 of the Royal Borough of [site address] [name] 2012 (CS) and Policy SI 2 of the London Plan 2021 (London Plan).

Collectively and amongst other things paragraphs 163, 165, 167 and 168 of the Framework state that the need to mitigate and adapt to climate change should be considered in assessing planning applications. The planning system should support the transition to a low carbon future and significant weight should be given to the need to support energy efficiency and low carbon heating improvements to existing buildings. This includes through the installation of heat pumps.

Amongst other things Policy D3 of the London Plan 2021 (London Plan), promotes a design-led approach which aims for high sustainability standards and delivery of appropriate amenity and environments that are comfortable and inviting for people to use. Developments should help prevent or mitigate the impacts of noise. CS Policy DM10 similarly states that proposals should have regard to the living conditions of the occupiers of neighbouring properties including avoidance of visual intrusion, noise and disturbance. From the evidence set out in the appellants appeal statement the [site address] [name] (SPD) is consistent with CS Policy DM10.

From my site visit and the evidence submitted I have no reason to dispute the agreed background noise levels of 33dB daytime and 28dB nighttime. The council has stated that the rating level of the noise from the air handling units by the cumulative sound emissions of the plant should be at least 5dBA lower than the existing background noise.

BS 4142:2014+A1:2019 ‘Methods for rating and assessing industrial and commercial sound’ (BS 4142) sets out guidance for where industrial or commercial noise is present or proposed and likely to impact a residential receptor. The guidance enables the effects of such noise on people nearby to be assessed and the associated risks to be minimised. It provides a methodology for determining an initial estimate of significance through subtracting the measured background noise level from the specific sound level of the source corrected for any distinctive acoustic characteristics. Typically, the greater the difference, the greater the magnitude of the impact.

BS 4142 advises that a difference of around +10dB or more is likely to be an indication of a significant adverse impact, whilst a difference of around +5dB is likely to be an indication of an adverse impact, depending on the context. Where the rating level does not exceed the background sound level, this is an indication of the specific sound source having a low impact, depending on the context. Context is defined as including the following factors: • The absolute level of sound. • The character and level of the residual sound compared to the character and level of the specific sound. • The Acoustic design measures.

The noise exposure hierarchy table at [name] 004 ID 30-004-20190722 of the Planning Practice Guidance provides further advice on noise and the effect it can have on living conditions.

The Council has not identified any national or local planning policies, supplementary advice or technical evidence which requires the cumulative rating level of the noise from the proposed ASHP’s and ACU, to be at least 5dBA lower than the ambient background noise level. The appellants have stated that the maximum noise level should be set at 30dBA, which was the level previously suggested by one of the council’s Environmental Protection Officer’s. This is slightly above the nighttime ambient noise level and I am conscious that nighttime noise can disturb sleep.

Having regard to the existing low background noise levels; the character and potential level of residual sound; and the acoustic design measures proposed it would be both appropriate and reasonable to restrict the noise generated cumulatively by the proposed ASHPs and ACU to no more than 28 dB LAeq. 15mins. when measured one metre from the closest habitable room window at [address]. This is on the basis that one of the closest windows to the proposed ASHPs and ACU serves a bedroom. This should result in the sound source having a reasonably low impact on the living conditions of the occupiers of [address].

The Technical Note – [name] prepared by Praxis in March 2023 advises that the ‘worst case’ noise generated by the proposed ASHPs and ACU, plus an allowance for acoustic feature correction would be 61dB. To address this the appellant appointed [name] to design an enclosure that would reduce the noise cumulatively generated by the ASHPs and ACU to an acceptable level.

Concerns were raised by the neighbour’s noise consultants that insufficient details had been provided and that the predicted noise reduction was unrealistic. In response the appellant confirmed that the intake and discharge attenuators would be 2.4 metres wide and that ample circulation space would be provided within the enclosure. The absorption coefficients would not exceed 1.0 and justification for a ground absorption rate of 0.5. The approximate sound reduction figures for the door were provided. They also acknowledged that plant noise modelling does not factor in the precise location and surroundings of a site and that the precise noise reduction that would be achieved by the proposed enclosure would not be known until fully installed.

The appellant also sought a review of the proposed ASHPs, ACU and acoustic enclosure. Rather than looking at manufacturers worst case scenarios, it focused on the nature and performance of the proposed ASHPs, the size and design of the acoustics enclosure and the siting of the units within it. The advice provided concludes that the proposed ASHPs and ACU together with the noise mitigation built into the proposed enclosure could provide an outcome that could meet the council’s requirements.

Taking the above factors into account, I am satisfied that the concerns raised by Trium on behalf of the occupiers of [address] have been satisfactorily addressed. This is provided the background noise levels do not exceed 28 dB LAeq. 15mins. when measured at a point one metres from the closest bedroom at [address]. This is a matter that could be secured through the imposition of a

The appellant, the Council and the occupiers of [address] have been consulted on the wording of the conditions set out in the attached schedule, which address some of the comments received. I have carefully considered other changes suggested by the Council and the occupiers of [address], who feel that the restriction of noise to no more than 28 dB LAeq. 15mins at any time, should also apply to the rear garden at [address].

The purpose of restricting noise levels to 28 dB LAeq. 15mins at any time within the closest bedroom at [address] is to minimise sleep disturbance. Given the proximity of this bedroom window to the boundary with [site address] , the noise restriction would also materially restrict noise levels within the gardens at [address]. For these reasons I consider it would be both unnecessary and unreasonable to further restrict noise levels within the gardens at [address]. Similarly, it would be unreasonable to further restrict noise levels within the garden at [address] in case the owners of that property decide at some time in the future that they would like to build an extension with a bedroom relatively close to the boundary with the appeal site.

It has been suggested that the ASHPs and ACU should not be used until the acoustic enclosure has been erected. This is unreasonable as the ASHPs provide electricity to the property for heat and water. Were the ASHPs to cause a statutory nuisance prior to the completion of the noise enclosure the Council has the ability to deal with the matter under other legislation. Following the completion of the acoustic enclosure and its subsequent testing the local planning authority would be able to take enforcement action against any breaches of conditions 3 and 4. Any changes to the acoustic enclosure following its completion would require the written consent of the local planning authority. It should be noted that the acoustic enclosure should be completed prior to December 2025 and the necessary noise testing would need to be undertaken during the winter when outside temperatures are typically low.

I conclude on the main issue that subject to the proposed conditions, the proposal would not have an unacceptable impact on the living conditions pf the occupiers of [address] in respect of noise and disturbance. Accordingly, it complies with Policy D3 of the London Plan, CS Policy DM10 and paragraph 135 of the Framework.

The resultant structure would be well screened within the rear garden environment by existing buildings, the boundary fence and planting and would not be visible from the street scene. For these reasons the proposal would not harm the character and appearance of the host dwelling, which is locally listed, or the surrounding area which is within [address]/[address] Strategic Area of Special Character.

I have assessed the conditions suggested by the Council against the tests set out in paragraph 55 of the Framework. A condition specifying the approved plans is necessary to provide certainty. The Council has suggested the imposition of a condition which requires the proposal to be carried out in accordance with the materials specified on the application form. As further details are set out in the appellants design and access statement and on drawing No.101 Rev.B they should also be referred to in the materials condition. This condition is both necessary and reasonable to ensure the proposal does not harm the character and appearance of the site and its immediate setting.

A condition which prevents the roof of the proposed acoustic enclosure from being used as a sitting out or other amenity area is necessary and reasonable to protect the privacy of the occupiers of [address].

Conditions which require the acoustic enclosure to be built within 4 months of this decision; restrict noise levels within close proximity to the existing closest bedroom window at [address]; and require a Noise Impact Assessment to be undertaken once the acoustic enclosure has been installed are both reasonable and necessary to protect the living conditions of the occupiers of [address]. Similarly, a condition which prevents the roof of the proposed acoustic enclosure from being used as an amenity area is necessary and reasonable in the interests of protecting the living conditions of the occupiers of [address].

Finally, as the ASHPs and ACU have already been installed there is no need to impose the standard time limit for commencing the development.

Having regard to the conclusion on the main issue and taking all other matters raised into account the appeal is allowed.

The development hereby permitted shall be carried out in accordance with the following approved plans and details: 20041-P222 [name] – [name] 31.05.2024, 20041-P204 REV A Location Plan and Proposed Site Plan Received 31.05.2024, 20041-P220 [name] Elevations, Floor and Roof plans Received 31.05.2024, 20041-P221 [name] Section A-A Received 31.05.2024, 20041-P223 [name] – [name] 31.05.2024, 20041-P224 [name] 31.05.2024, 20041-S103 [name] and Site Plan Received 31.05.2024’ 20041-P222 [name] – [name] 31.05.2024, 20041-P204 REV A Location Plan and Proposed Site Plan Received 31.05.2024, 20041-P220 [name] Elevations, Floor and [name] 31.05.2024, 20041-P221 [name] A-A Received 31.05.2024, 20041-P223 [name] – [name] 31.05.2024, 20041-P224 [name] 31.05.2024, 20041-S103 [name] and Site Plan Received 31.05.2024, [name] - 22-08-2024 Received 06.09.2024, 101-B Plan and [name] 23.07.2024 [name] of [name] - Temple (2) Received 14.10.2024, [name] of [name] - Temple 04/10/2024 Received 14.10.2024, [name] letter Received 06.09.2024, [name] - 22-08-2024 Received 06.09.2024, The Gatehouse Report - Rev9- [name] 06.09.2024, [name] - AM000JXVHGR Received 06.09.2024, AM220JXVHGR [name] 06.09.2024, AM140JXVHGR [name] 06.09.2024, 92309040 Drg101B Plan and [name] 18.08.2024

The development to which this permission relates shall be carried out in accordance with the materials specified on the application form, [name].101 223Rev.B and set out in the Design and [name] unless otherwise agreed in writing by the local planning authority.

i. Within 4 months of the date of this decision the acoustic enclosure hereby permitted shall be erected and shall thereafter be retained and maintained such that the noise level specified in part (ii) of this condition is not exceeded at any time; and ii. The level of noise emitted from the air source heat pumps and air conditioning unit hereby permitted shall not individually or cumulatively exceed 28 dB LAr,Tr. 15mins at any time when measured one metre from the current window of bedroom 5 of [address].

A post-installation Noise Impact Assessment prepared by an independent acoustic consultant demonstrating that the noise levels stated in condition 3 above have been achieved must be submitted to the Local Planning Authority for approval in writing within 2 months of the date of the erection of the acoustic enclosure. If the noise levels exceed the above noise levels prescribed in condition 3 then the equipment and enclosure approved by the permission must be removed in its entirety from the application site within 3 months of the date of the refusal of the necessary discharge of condition application, unless otherwise agreed in writing by the local planning authority to facilitate adjustments to the noise enclosure hereby permitted so that it complies fully with condition 3 i. & ii.

The flat roof area of the development to which this permission relates shall not be used as a roof garden, balcony, seating area or other similar amenity area, and shall not be accessed except for the purpose of maintenance or in the case of emergency. ***End of Schedule***